LAUSR

Intrinsic optoelectronic properties of atomically precise graphene nanoribbons (GNRs) remain largely unexplored because of luminescence quenching effects that are due to the metallic substrate on which the ribbons are grown. We probed excitonic emission from GNRs synthesized on a metal surface with atomic-scale spatial resolution. A scanning tunneling microscope (STM)–based method to transfer the GNRs to a partially insulating surface was used to prevent luminescence quenching of the ribbons. STM-induced fluorescence spectra reveal emission from localized dark excitons that are associated with the topological end states of the GNRs. A low-frequency vibronic emission comb is observed and attributed to longitudinal acoustic modes that are confined to a finite box. Our study provides a path to investigate the interplay between excitons, vibrons, and topology in graphene nanostructures. Description Optical properties revealed Graphene nanoribbons (GNRs) are typically grown on metallic surfaces such as silver or gold. The presence of a metallic substrate makes the optical properties of GNRs difficult to study. To avoid this issue, Jiang et al. grew armchair-edge GNRs on a gold surface and used the tip of a scanning tunneling microscope to transfer them to an adjacent insulating surface. The researchers then induced fluorescence in the GNRs, revealing signatures of topological edge states, as well as a rich vibronic spectrum. —JS Scanning tunneling microscope–induced luminescence is used to study the optical properties of decoupled graphene nanoribbons.